This invention relates to passive anti-theft devices for vehicle ignition locks.
Vehicle manufacturers have built a number of anti-theft features into the ignition locks of cars and trucks. When the key is taken out, the steering wheel is locked from turning and the gear shift lever is prevented from moving. So, theoretically, it's impossible to drive the car. The Achilles heel of this approach has been that it is relatively easy for an auto thief to pull out the cylinder of the ignition lock and bypass these measures.
To circumvent this problem it has been suggested, e.g. in U.S. Pat. Nos. 3,916,658 and 4,167,222, to surround the steering lock with a hardened metal casing while providing key access to the rotating lock cylinder by mounting a hardened rotatable cap with a slot that permits insertion of the key to turn the lock, yet guards against pulling the lock cylinder out.
One particularly bothersome problem of this approach is that if the operator does not insert the key fully, but then attempts to turn on the ignition by turning the cap, the portion of the key that is captured in the slot tends to turn with the cap while the portion that is captured in the lock cannot turn. Because of the mechanical advantage provided by the relatively large cap, the key is either bent or broken.
One object of this invention is to prevent such key breakage.
A further problem is providing and maintaining proper alignment of the key access through the armor cap with the rotating lock cylinder. If the access is not aligned, or if it slips out of alignment, the lock cylinder can jam during operation with resulting damage to the vehicle, e.g. a burned out starter motor.
A further object of the invention is to prevent such misalignment.